Evolution of Human Diet
For many years, food available from vegetable and animal sources was low in fat (less than 25% of total energy intake), for it was of a wild type and because it was mostly eaten raw or grilled. It was source of about equal amount of saturated and polyunsaturated fatty acids as well as of ω6 and ω3 isomers (P:S=ω6:ω3=1:1).
When rudimentary agriculture began to slowly bring changes in dietary habits, making food from animal origin (meat, fish, milk, eggs) more present in the daily diet, the contribution of cholesterol and saturated fatty acids to the total fat content proportionally increased.
However, the ω6:ω3 ratio remained relatively constant because traditional animal husbandry and fish culture did not widely differ in terms of feeding from former wild-type life, i.e. because the animals had large access to green-leaf vegetables (livestock) and phytoplanktons (fish).
Deviations from human food standards came readily into prominence at the turn of the century with the emergence of the modern agriculture and vegetable-oil industry.
Emphasis on ω6-rich grains fattening of domestic livestock and fishery and on partial selective hydrogenation of ω3-rich vegetable oils results in a dramatic decrease in the amount of ω3 fatty acids available to humans and to a not-less dramatic increase in the contribution of total fat and trans fatty acids to the daily energy supply of the human diet.
The drastic deviation operated some 150 years ago in human food habits changed the ω6:ω3 ratio that was about 1:1 during the evolutionary period to a now estimated imbalance of about 10-11:1 for food from vegetable source and closer to 20-25:1 for mixed food from vegetable and animal sources. Meanwhile, the human genetic constitution remained relatively unchanged and did not cope with this brutal pace of change in the food chain.
TABLE 1Time (years)−4.000.000−10.000185019502000Total25%30%35%40%fatP:S1:10.9:10.75:10.5:1ω6:ω31:1  10:1 20:1
Table 1 gives a scheme of the relative contribution of different dietary fatty acids (saturated fatty acids, ω6 and ω3 polyunsaturated fatty acids) to the human diet and possible changes subsequent to modern agriculture and industrial food processing, involving fattening of animal husbandry and hydrogenation of fatty acids.
In the meantime, wild animals, which were still left grating on green leaves and wild plant seeds, continued to exhibit balanced essential fatty acid ratio's in their fat depots, independently from the species they belong to (Crawford, M. A. et al. (1989) “The food chain for n-6 and n-3 fatty acids with special reference to animal products”, in Dietary ω3 and ω6 Fatty Acids—Biological Effects and Nutritional Essentiality (Galli, C. & Simopoulos, A. P., eds) NATO ASI Series A: Life Sciences Vol. 171, pp.5-19, Plenum Press, New York, ISBN 0-306-43231-5).
Link with Modern Degenerative Diseases
Today, ω6 and ω3 PUFA are known to be essential in minimum amounts (see table 2 for adequate intake) for normal growth and development of humans. Their relative concentration or fractional ratio (ω6:ω3) in food regulates the in vivo metabolism of lipoproteins, the fatty acid composition of cell membranes and the synthesis of some important biological mediators, the eicosanoids, which are essential to cell communication and global homeostasis. Scientific evidences suggest that at least some human degenerative diseases have a food link and that the highly unbalanced modern dietary ω6:ω3 ratio, as well as the strong contribution of total fats (more than 35% of total energy intake) and of saturated fatty acids (P:S=0.5:1, including trans isomers) to the daily energy intake, may well have a direct implication into the appearance of some characteristic diseases of our modern society, i.e., cerebro- & cardiovascular diseases, coronary heart affections, cancers, diabetes, high blood pressure, chronic inflammatory and auto-immune diseases. More specifically, arachidonic acid, the ω6 long-chain fatty acids derived from linoleic acid and/or obtained directly from food of animal origin, has been shown to effectively accumulate in modern man tissues when ingested in excess (A. T. Simopoulos (1991) Omega-3 fatty acids in health and disease and in growth and development, Am. J. Clin. Nutr. 54, 438-463). Consequently, arachidonic acid-derived eicosanoids have taken the lead in cell and tissue behaviour of modern man with all the deleterious consequences for health.
Scientific and epidemiological evidence seems to confirm that excess ω6 fatty acids in modern man diet could well be one of the major culprit for reduced health performance in ageing.
The “Balanced Diet” Notion
Galli & Simopoulos (“General recommendations on dietary fats for human consumption”, in Dietary ω3 and ω6 Fatty Acids Biological Effects and Nutritional Essentiality (Galli, C. & Simopoulos, A. P., eds) pp. 403-404, North Atlantic Treaty Organisation Advanced Science Institute Series, Plenum Press, New York & London (1988)) defined a well-balanced diet as one that, among other things, provides max. 30% energy as fat together with a large proportion of monounsaturated fatty acids, an even distribution of saturated and polyunsaturated fatty acids (S:M:P=1:6:1), a ratio between ω6 and ω3 isomers not exceeding 5 to 1 (ω6:ω3≦5:1), and an optimal amount of 350-400 mg ω3 long chain polyunsaturated fatty acids (ω3 LC-PUFA).
In a recent workshop held at The Cloisters, National Institute of Health (NIH) in Bethesda, Md., USA, Apr. 7-9, 1999, an Expert Panel led by Prof. A. T. Simopoulos established the following adequate intakes for ω6 and ω3 fatty acids in adults (table 2).
TABLE 2Adequate Intakes (AI) for Adults% totalFatty AcidAbbrevFormulaGrams/day*Cal/daycal.LinoleicLAC18:2ω64.44402acidα-linolenicLnAC18:3ω32.22201acidEPA + DHAω3 LCPC20/22:5/6ω30.4440.2*2000 kcal diet
It is seen that there is a clear trend towards re-adopting the historically-established, naturally-occurring lipid ratios settled by Nature 4 million years ago as those which must be optimally fit for human consumption. Quite remarkably, these modern recommendations for amounts and ratios of lipids in human diet are based on meta-analysis of epidemiological and clinical studies of the long term relationship between dietary habits and degenerative diseases in human.
Optimum dietary lipid pattern can be reached through substitution of ω6-rich for ω3-rich vegetable oils and enrichment of modern-type diets with greens, leaves and fish, but enrichment does in fine mean adding-up on fat.
Ideally, edible animal tissue lipids should also comply with these scientifically established evidence since pre-formed arachidonic acid from animal origin is known to incorporate very effectively in tissue lipids (Lands, W. E. M. (1997) Two faces of EFA, Inform 8, 1141-1147). Essentially, there is no scientific evidence for a need in dietary arachidonic acid in normal people. A very important aspect of wild-type animal tissue is that they favour ω3 versus ω6 long-chain phospholipids and contain substantially lower amount of arachidonic acid in comparison to their domesticated equivalent.
Scientifically and naturally established evidences suggest that healthy food from animal origins is of the wild or game-type, lean and balanced in essential fatty acids, low in arachidonic acid.
Eggs as Food
Eggs are generally recognised as source of highly bio-available and valuable nutrients.
As a source of essential amino-acids, eggs are remarkable in that they are in perfect agreement with adult human needs; they are also a rich source of beneficial branched amino-acids (table 3).
TABLE 3Essential amino-acids in eggs and human needs(+)mg/100 g**RDA (mg)Essential amino acids(two 60-g eggs)70-kg adultHistidine275—*Isoleucine675840*Leucine10751120Lysine875840Cysteine + Methionine712.5700Tyrosine + Phenylalanine1162.51120Threonine587.5560Tryptophan212.5210*Valine825980   Lysine      Cysteine    +    Methionine  1.231.20*BCAA: branched chain amino-acids**RDA: recommended dietary allowances (National Academy of Sciences, U.S.A., 1974)(+)FAO Food and Nutrition Paper 51(1990) Protein quality evaluation (Content in mg/g protein × 12.5)
Carbohydrates mainly appear in eggs as glucose and glycoproteins (table 4).
TABLE 4Carbohydrates in eggsmg / 100 g (two 60-g eggs)Albumen (68-g)Yolk (32-g)Total (100-g)Free sugar*260260520Oligosaccharides**330110440Total590370960*mainly D-glucose -**N- & O-glycans in albumen, sialoglycans in yolk (Sugino, H., Nitoda, T. and Juneja, L. R. (1997) General Chemical Composition of Hen Eggs, in “Hen Eggs, Their Basic and Applied Science” (Yamamoto, T., Juneja, L. R., Hatta, H. & Kim, M. eds) CRC Press Inc., Ch. 2, pp. 13-24).
Lipids in egg yolk appear as a mixture of neutral and polar lipids; their fatty acids are either long (C16-18) or very long (C20-22) carbon chains (table 5).
TABLE 5Lipids in eggsLipidg / 100 g (two 60-g eggs)fractionsTriglyceridesPhospholipidsCholesterolTotalWeight6, 92, 70, 43010  contribution% fatty acid9672~085.5Fatty acidsC16-C18C16-C22—C18type
Vitamins and minerals are omnipresent at relatively high concentration in eggs (table 6).
TABLE 6Vitamins, minerals and oligoelements in eggs andhuman needsVitaminsNameRDI*100 g-egg% RDIVit. AaRetinol1.51500.192112.7*Vit. DbCalciferol0.01000.001212.0Vit. EcAlpha-tocopherol20.00001.40007.0*Vit. K1PhylloquinoneVit. B1Thiamin1.50000.06204.1Vit. B2Riboflavin1.70000.508029.9*Vit. B3dNiacin20.00000.07400.4(Pp)*Vit. B5Panthotenic acid10.00001.254012.5Vit. B6Pyridoxin2.00000.14007.0Vit. B8 (H)Biotin0.30000.02006.7Vit. B9 (M)Folic acid0.40000.046011.5Vit. B12Cyanocobalamine0.00600.001016.7Vit. CeAscorbic acid60.0000MineralsName2000 Cal100 g-egg% RDICaCalcium100050.05.0PPhosphorus1000178.017.8MgMagnesium40010.02.5NaSodium126.0ClChlorine174.2KPotassium120.0SSulfur164.0OligoName2000 Cal100 g-egg% RDIFeIron18.001.4408.0ZnZinc15.001.1007.3SeSeleniumCuCopper2.000.0140.7IIodine0.150.04832.0MnManganese0.024MoMolybdenAll numbers in mg; 100-g eggs stands for the edible part of two 60-g-eggsRDI: Reference Daily Intake = average values for healthy Americans over 4-y-oldRDI* given for a 2000 Cal-diet*accessory- or conditionally essential nutrienta) retinol equivalent: 1 mcg retinol/β-caroten or 3.3 IUb) calciferol: 1 mcg or 40 IUc) alpha-tocopherol equivalent (α-TE): 1 mg d-alpha-tocopherol or 1.49 IUd) niacin equivalent: 1 mg nicotinic acid (or nicotinamide) or 60 mg tryptophane) ascorbic or dehydroascorbic acid
The weight-distribution of amino-acids, carbohydrates and lipids is genetically encoded in eggs whilst that of vitamins, minerals and fatty acids is sensitive to their concentration in the bird's diet.
The egg lipid composition has often been criticised in terms of its relatively high concentration in saturated fatty acids and cholesterol compared to total energy content. The scientifically-proven relationship (known as the “lipid hypothesis”) between high dietary CSI (cholesterol-saturated fat index) and relatively higher risk of cardio- and cerebrovascular diseases has often supported the critical evaluation of cholesterol content in food. Cell membranes of animal tissues differ from those of plant tissues in that they contain cholesterol and phospholipids bearing long chain polyunsaturated fatty acids. Egg yolk lipids conform to this rule: cholesterol and long-chain polyunsaturated fatty acids happen to appear in a ratio close to 1:1 (0.5 mM each in egg yolk) and the latter occur at the characteristic sn-2 position of tissue phospholipids. There is thus nothing special or “wrong” about the cholesterol level in egg—it just has to do with its primary function, i.e. to support the development of Life in avian. Cholesterol in egg yolk is almost a constant whatever the type of feed served to the chicken. However, the content of polyunsaturated fatty acids can be increased at the expenses of that of saturated and monounsaturated fatty acids by simple dietary means.
While amounts of saturated, mono-unsaturated, ω3 and ω6 polyunsaturated fatty acids have been separately varied in previous egg production and the effect of these minor changes on human blood lipid balanced were already described, eggs wherein all fatty acid and lipid fractions are controlled to result in a product which is compatible with a healthy diet defined as that one designed by Nature in the wild, were never produced nor described.
Aims of the Invention
The present invention aims to provide eggs obtained from domesticated birds, in particular layers, said eggs comprising an improved lipid balanced profile in order to result in a product compatible with healthy diet for humans and animals comparable to the one designed by nature in the wild.
Another aim of the present invention is to provide such safe and improved eggs and food compositions comprising such eggs that may be consumed as part of a balanced diet in reasonable quantity, as recommended by national and international heart foundations, and that sustain consumer's health in the long term.
A further aim of the present invention is to provide a feed composition of exclusive vegeterian origin and a feeding method for poultry, in particular layers, from which said eggs having an improved lipid balanced profile may be obtained.
A last aim of the present invention is to provide such feed composition and feeding method for feeding poultry, in particular layers, that can be maintained in various conditions for the production of such eggs.